FIG. 1 is a sectional view of a prior-art engine starting and charging device disclosed in Laid-Open Japanese Patent No. sho 61-54949. In FIG. 1, a starting and charging device body 1 is constituted of revolving-field poles 2a, 2b, field windings 3, an armature core 4, an armature winding 5, and a crank angle detector 6 as major components.
A pair of revolving-field poles 2a, 2b are comb-shaped ones produced of a ferromagnetic material, and are coupled as a unit through a non-magnetic ring 7 such that these magnetic pole sections are disposed alternately in the circumferential direction.
The revolving-field pole 2a functions also as a flywheel, which is fitted on a crankshaft 8 as a revolving shaft of the engine, and firmly secured by a bolt 9 on the end of this crankshaft 8.
In the side section of the revolving-field pole 2a are formed cutouts 10 which, combined with a crank angle detector 6, are used for the detection of the crank angle. There are provided the same number of cutouts 10 as the revolving-field poles 2a at equal intervals on the circumference.
The width of this cutout 10 in the circumferential direction makes an angle equal to about one half of 360 degrees divided by the number of the cutouts.
The revolving-field poles 2a, 2b described above are so designed as to be excited by energizing the field winding 3, which is installed on the field core 11.
This field core 11 is secured by a bolt not illustrated to a rear plate 12, facing the revolving-field pole 2a across a slight gap a provided in the axial direction, and facing the revolving-field pole 2b across a slight gap b.
The field winding 3 is provided on the fixed side, dispensing with a collector ring; however, because the current flowing into the field winding 3 is much less than the current in the armature winding 5, it is possible to energize it through a collector ring and brushes.
The armature core 4 is formed by laminating silicon steel sheets, within the inner periphery of which are provided a large number of slots for setting the armature winding 5 therein. The armature winding 5 is of a three-phase distributed winding type as a common commutatorless motor.
The armature core 4 is fitted to a mounting frame 13, positioned to the mounting frame 13 by a key not illustrated, and locked from turning. At this time, the armature core 4 is secured by a spacer 14 in the axial direction to the mounting frame 13 through a spring ring 15.
Furthermore, the mounting frame 13 is mounted by a bolt 16 to the rear plate 12. The rear plate 12 is attached to an engine body which is not illustrated.
In the meantime, the crank angle detector 6 described above functions as a signal source which operates the armature current switching circuit. Here, a signal-generating proximity switch is used.
This proximity switch is mounted on the rear plate 12 such that its detector element will face on the circumferential line where the cutout 10 of the revolving-field pole 2a is disposed, and signal generating conditions vary with a change in inductance at the cutout section and non-cutout section of the revolving-field pole 2a, thus outputting a binary signal "1" or "0" correspondingly to the crank angle (field pole position). When a three-phase armature winding 5 is employed, three crank angle detectors 6 will be used.
A clutch 17 serves to interrupt the transmission of power between the crankshaft 8 and a transmission drive shaft 18. This clutch 17 uses a diaphragm spring clutch consisting of a clutch disc 19, a pressure plate 20, a diaphragm spring (disc spring) 12, wire rings 22, 23, and a clutch cover 24.
The clutch cover 22 is mounted by bolts 25 to the revolving-field pole 2a which serves also as the flywheel.
Subsequently, operation at the time of starting will be explained. When the key switch (not illustrated) is placed in the START position with the engine left stationary, the current flows from the battery (not illustrated) into the field winding 3 and the armature winding 5, thereby producing a torque in the revolving-field poles 2a, 2b and accordingly turning the crankshaft 8 which is directly coupled therewith.
As the revolving-field poles start turning, the crank angle detector 6 detects the position of the revolving-field poles, actuating the armature current switching circuit (not illustrated) such that the speed of the revolving field formed by the armature winding 5 will be the same as the speed of rotation of the revolving-field poles, and the revolving-field poles 2a, 2b, receiving the torque, will further accelerate.
Since a great starting torque is obtainable through positive feedback operation, directly-coupled drive is able to the engine in a short time.
Next, when the key switch is placed in the IGNITION position after the engine has started, the starting and charging device body 1 operates as an a.c. generator, the power generated being converted into the direct current by a diode (not illustrated) and supplied to the battery and electrical equipment on the motor vehicle.
The operation of the clutch 17 is as follows. When the clutch pedal (not illustrated) is not depressed, the tension of the diaphragm spring 21, as well known, is added by leverage to the clutch disc 19 mounted on the transmission drive shaft 18 through the pressure plate 21, thus pressing this clutch disc 19 against the side of the revolving-field pole 2a to connect the clutch 17.
Also, when the clutch pedal is depressed, a sleeve which is not illustrated slides in the axial direction, pressing the central part of the diaphragm spring 21 in the direction of the arrow C. Therefore, the diaphragm spring 21 will deflect on the wire rings 22, 23 as a fulcrum, removing the pressure applied to the clutch disc 19. Thus the clutch 17 will become disconnected, interrupting power transmission between the crankshaft 8 and the transmission drive shaft 18.
The starting and charging device body 1 and the clutch 17 are formed as one body by directly connecting the revolving-field pole 2a of the starting and charging body 1 to the engine crankshaft 8 and further by using this revolving-field pole 2a as a carrier of the clutch 17 for connection and disconnection between the crankshaft 8 and the transmission drive shaft 18.
FIG. 2 is a sectional view showing another example of the prior-art engine starting and charging device, in which the same numerals are used for the same parts appearing in FIG. 1 described above, their explanation being omitted.
In FIG. 2, on the bracket 13 are positioned and secured the armature core 4, the field core 11 and the crank angle detector 6. This bracket 13 is mounted by bolts 26 to a cylinder block 28 through a gasket 27; the field core 11 faces the revolving-field poles 2a, 2b with slight gaps a and b provided in the diametrical direction.
In the above-described prior-art starting and charging device, because the whole body of the device is hermetically enclosed, directly affected with the temperature increase of engine, and in addition, the atmospheric temperature of the hermetically enclosed chamber will be increased by a great deal of frictional heat produced by the connection and disconnection of the clutch disc 19 and the clutch 17 and the heat of resistance loss caused by a tremendous current flowing into the armature winding 5 and the current flowing into the field winding 3.
However, the device has such a problem that no means for cooling such as a cooling fan is provided, and if the means for cooling is mounted, a cooling effect in the hermetically enclosed chamber will be low, resulting in an excessive temperature rise at each part, deteriorated quality in respect of heat resistance, a decreased current in the field winding 3 in respect of performance, an excessive degradation of operating characteristics, and consequently in a failure in obtaining a desired starting torque or output current.
FIG. 3 is a sectional view of an a.c. generator for motor vehicles that has a fan as a cooling means. In FIG. 3, numeral 31 is a revolving shaft, on which a pulley 32 is fixedly secured. Numeral 33 is a rotor secured on the revolving shaft 31, and is of the following constitution. Numeral 34 is a revolving-field core, and numeral 35 is the other revolving-field pole, from which a plurality of pole pawl sections 35a are disposed at intervals in the circumferential direction.
Numeral 36 is a non-magnetic support ring secured on the circumference of the pole pawl sections 35a, and numeral 37 is the other revolving-field pole secured by this support ring 36, with a plurality of pole pawl sections 37a disposed at intervals in the circumferential direction, alternately between the above-mentioned pole pawl sections 35a.
Numeral 38 is a fixed field core disposed between the revolving-field core 34 and the other revolving-field pole 37 with an air gap provided therebetween; numeral 39 is a field winding held by this field core 38; and numeral 40 is a fixed armature core, which holds an armature winding 41 in slots.
Numeral 42 is a front bracket which supports the revolving shaft 31 through a front bearing 44 and combinedly supports the armature core 40. In this front bracket 42 is provided a cooling air outlet hole 42a.
Numeral 43 is a rear bracket which combinedly supports the armature core 40. It supports the revolving shaft 31 through a rear bearing 45 and also fixedly supports a field core 38. In this rear bracket 43 is provided a cooling air inlet hole 43a.
Numeral 46 designates a rectifier for converting a.c. power from the armature winding 41 into d.c. power; numeral 47 is a voltage regulator which detects the generator voltage, controls the exciting current, and regulates the terminal voltage to a specific value; and numeral 48 is a fan fixed on the revolving shaft 31.
In the prior-art device described above, the revolving shaft 31 is turned through a belt (not illustrated) and a pulley 32 by the revolution of the engine on the motor vehicle. The a.c. voltage led to the armature winding 41 is regulated to a specific value by means of the voltage regulator 47, thus supplying the d.c. rectified power to the field winding 39 and at the same time to a load such as the storage battery.
In the meantime, as the fan 48 rotates, the cooling air is drawn in at the inlet hole 43a of the rear bracket 43, thus ventilating and cooling the machine interior, being drawn out at the outlet hole 42a of the front bracket 42, and being discharged by the fan 48.
There is, however, a problem that the fan 48, insufficient in cooling capacity, can not sufficiently cool the armature winding 41, the rectifier 46, the voltage regulator 47 and the field winding 39; the output current can not easily be increased on account of limited heat resistance; and the field winding 39 is insufficiently cooled, with the result that the output current decreases in excess.
In the meantime, although there is such a concept as the adoption of a large fan for the purpose of improving the cooling capacity of the fan 48, there still exists a problem in respect of mountability and noise. Since the fan 48 has a limited cooling capacity as described above, there also exists a problem that it is difficult to increase the output current and a large decrease in output must be taken into consideration in designing the fan.
In the meantime, as disclosed in U.S. Pat. Specification No. 4,295,067, the rotating electric machine has a heat pipe projecting out of a housing, but has no sufficient cooling capacity.
Furthermore, as disclosed in Laid-Open Japanese Pat. No. Sho 59-83557, the rotating electric machine which has a coolant passageway formed along the outer periphery of a stator core and is cooled with cooling air from a cooling fan and a coolant flowing in the above-mentioned coolant passageway, has sufficient cooling capacity but is of complicated constitution and costly.